The present invention relates to the remote inspection of pipeline systems and particularly, though not exclusively, to a method for the remote detection of pipeline blockages and leakage.
Power plants, chemical processing plants and oil processing plants typically include many pipes, often arranged in complex interconnecting networks. In order to maximise operational efficiency, these plants will often be run without interruption twenty-four hours per day and seven days per week. In these circumstances, it will not be possible to access the interior of the pipes during plant operation. This means that visual inspection of the interior of the pipes requires interruption of the plant operation, in most situations leading to a loss of production and cost penalties.
Several methods have been developed for inspecting the interior of pipes without requiring internal access to the point of inspection. One known method is to direct ultrasound through the pipe wall and detect the reflected ultrasound. The presence of an obstruction or leak in a pipe may be indicated by the characteristics of the detected ultrasound. A principal disadvantage of using ultrasound in this way is that only a small section of the pipe can be examined at one time i.e. the inspection is limited to the short length of the pipe at which the ultrasound is directed. Therefore, the inspection of a long pipe, or worse a pipeline network, will occupy a considerable amount of time since the ultrasound generator and detector must be placed adjacent to each section of the pipe which needs to be examined. Moreover, there are many situations in which the outer wall of the pipe will not be easily accessible as may occur, for example, if a pipe passes through a radioactive area in a nuclear power station. Clearly, it would be difficult (or impossible) to use the localised ultrasound method could not be used to inspect these pipes.
E. S. Morgan (Materials Evaluation, pg. 926-930, Vol. 39, September 1981) has described an acoustic detection apparatus used to detect the presence of a blockage in a pipe. The apparatus comprises a loudspeaker and a microphone to be located at one end of an open pipe which, for example, may be a cooling pipe in a power station. An acoustic pulse generated at the loudspeaker propagates along the pipe, is reflected from the open end of the pipe and is detected by the microphone. The signal detected by the microphone is passed to an oscilloscope which displays a trace that is synchronised to the generation of the pulse at the loudspeaker. The trace will show a peak which corresponds to the entrance of the pipe and a further peak which corresponds to the opening at the far end of the pipe. The appearance of any intermediate peak can be interpreted as indicating that a blockage exists in the pipe. The location of the blockage can then be determined from the position of the intermediate peak relative to the entrance peak and the peak which corresponds to the far end of the pipe under investigation.
The method described by Morgan may be used to test a single straight pipe, or a single pipe having several bends. The method suffers from the disadvantage that it is not applicable to pipe networks.
It is a principal objective of the present invention to provide a method of pipeline inspection which may be used to test a pipe network.
According to a first aspect of the invention there is provided a pipe inspection apparatus comprising an acoustic source for location at a first position in a pipe or pipe network, one or more acoustic or pressure detectors for location at one or more positions in the pipe or pipe network, means for recording and/or displaying a signal detected by the one or more detectors following the generation of an acoustic pulse, and means for allowing the comparison of the detected signal with a predetermined reference signal, differences between the detected and reference signals being indicative of a blockage or leakage in the pipe or pipe network.